How to determine the number of observations if running a panel data analysis using mixed models?

Well, firstly, I'm a bit confused since I cannot see the number of observations of my analysis, more precisely, I just have the number of df and, actually, I was wondering if I have to calculate the number of observations for my analysis on my own based of the denominator df?

Furthermore, I want to conduct a panel data analysis using the FEM for countries ( my panel is unbalanced) and, therfore, was wondering if I have to consider the countries as factors as well (and also the year-dummies)? I hope you can help with it as soon as possible.